Abstract We present observations of methanol lines in a sample of
Class 0 low mass protostars. Using a 1-D radiative transfer model,
we derive the abundances in the envelopes. In two sources of the
sample, the observations can only be reproduced by the model if the
methanol abundance is enhanced by about two order of magnitude in
the inner hot region of the envelope. Two other sources show similar
jumps, although at a lower confidence level. The observations for
the other three sources are well reproduced with a constant
abundance, but the presence of a jump cannot be ruled out. The
observed methanol abundances in the warm gas around low mass
protostars are orders of magnitude higher than gas phase chemistry
models predict. Hence, in agreement with other evidence, this
suggests that the high methanol abundance reflects recent
evaporation of ices due to the heating by the newly formed star.
The observed abundance ratios of CH3OH, H2CO and CO are in
good agreement with grain surface chemistry models. However, the
absolute abundances are more difficult to reproduce and may indicate
the presence of multiple ice components in these regions.